Flareless tube coupling



Feb. 11, 1964 H. SCHMOHL 3,120,969

FLARE LESS TUBE COUPLING Filed May 12, 1959 I50. I 9 IO 23 I //W [/YG"i4 7 a 210 20 2| I INVENTOR.

LELAND H. SCHMOHL BY ATTORNEYS United States Patent 3,120,69 FLARELESSTUBE COUPLING Leland H. Sehmohl, Moreland Hills, Ohio, assignor t0Parker-Hannifin Corporation, Cleveland, Ohio, a corporation of OhioFiled May 12, 1959, Ser. No. 812,623 4 Claims. (Cl. 285-341) The presentinvention relates generally as indicated to a fiareless tube couplingand more particularly to a flareless tube coupling of the type whichemploys a sleeve or ferrule which at one end is adapted to be radiallycontracted into gripping and sealing engagment with the sur face of thetube which is to be joined to the coupling assembly, and which, at theother end, is adapted to be deformed into frictional engagement with thetube in a manher so as to effectively dampen vibrations in the tube at azone axially spaced from the zone where the ferrule is in gripping andsealing engagement with the tube.

It is a principal object of this invention to provide a simple threepiece liareless tube coupling, viz., a body, a nut, and a ferrule,characterized in that these parts are so formed that tightening of thenut effects axial advance of the ferrule against the Hare mouth of thebody to cause radial contraction of the front end of the ferrule intogripping and sealing engagement with the tube and radially contractionof the rear end of the ferrule into vibration damping contact with thetube.

It is another object of this invention to provide a flareless tubecoupling that has a ferrule provided with a tubular gripping and sealingend radially outwardly offset with respect to the rearwardly adjacentportion so as to be readily contractible up to the point where propergripping and sealing contact is obtained but not so readily contractiblethereafter whereby overtightening may be avoided.

it is another object of this invention to provide a flareess tubccoupling in which the ferrule thereof has a head at its rear or outerend engaged by the nut and is formed with an annular groove adjacentsaid head which is arranged to cause said head to turn in and cause thegrooved portion to contract against the tube into vibration dampingcontact therewith.

It is another object to provide a flareless tube coupling in which thesleeve has an enlarged head at the rear end thereof, with a groovedportion adjacent thereto, which head has an end surface initiallyengageable in line contact at its outer diameter with a shoulder surfaceon the nut, and in which tightening of the nut turns the sleeve head tocontract the grooved portion against the tube in vibration dampeningcontact therewith, and in which excessive turning in of the sleeve headclue to excessive tightening of the nut is avoided by reason of fullsurface engagement being established between said nut and sleevesurfaces.

It is another object to provide a flareless tube coupling in which thesleeve has an enlarged head at the rear thereof with a grooved portionadjacent thereto, and which head is deformable by contact with the nutso as to cause the grooved portion to contract into engagement with thetube, and said sleeve has a cylindrical front section which is readilydeformable by a tapered surface of the fitting body into tight grippingand sealing engagement with the tube, and in which the sleeve has atapered intermediate portion with the ends of said intermediate taperedportion being of lesser and greater diameter respectively than saidcylindrical portion, whereby upon normal tightening of the nut thetapered intermediate portion will remain out of contact with said bodytaper immediately adjacent the cylindrical portion but will contact thebody taper between the ends of said tapered intermediate portion toprevent uncontrolled expansion of said intermediate portion and forrapidly increasing the amount of torque required to turn the nut andthus provide a home feeling when the nut has been tightened the properamount.

It is another object to provide a flareless tube coupling in which thesleeve has a cylindrical front portion counterbored to provide anannular cutting edge longitudinally spaced from the front end of thesleeve, and in which the sleeve has an intermediate tapered portion,said tapered portion being of smaller diameter than said cylindricalportion at the region adjacent thereto so as to form a neck slightlyrearwardly of said cutting edge, said cylindrical portion beingcontractible by contact with a tapered mouth in the fitting body, saidneck facilitating contraction of said cylindrical portions in the regionof said cutting edge whereby the latter is contracted into grippingengagement with the tube.

Other objects and advantages of the present invention will becomeapparent as the following description procoeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principle of the invention may beemployed.

In said annexed drawing:

FlG. 1 is a side elevation view of a flareless tube coupling assemblyconstituting the present invention;

FIG. 2 is a much enlarged fragmentary radial crosssection view showingthe relative positions of the coupling parts in the finger-tightposition of the nut thereof; and

FIG. 3 is a similar enlarged fragmentary radial crosssection viewshowing the fully assembled condition of the coupling parts with theferrule contracted to make firm gripping and sealing engagement with thetube and sealing engagement with the flare mouth of the body at one endand vibration damping engagement with the tube at the other end.

Referring now more particularly to the drawing, the flareless tubecoupling herein comprises a body 1 provided, for example, with awrench-engaging portion 2 between its ends and tapered pipe threads 3 orthe like, and uniform pitch diameter male threads 4 at its respectiveends, and a nut 5 formed with female threads 6 engaged with threads 4.

As clearly shown in FIGS. 2 and 3, the body 1 is formed with a bore 7therethrough, an internal abutment shoulder 3 for an end of a tube T, acounterbore 9 adjacent said shoulder 8, and a countersink or flare mouth11 which, as hereinafter explained, constitutes a cam surface.

On the other hand, the internally threaded nut 5 is formed with a bore11, through which the tube T extends, and with an internal shoulder 12which preferably is tapered as shown.

Between the body 1 and nut 5 and surrounding the tube T and disposed toengage the flare mouth 10 of the body 1 and the tapered internalshoulder 12 of the nut 5 is a sleeve or ferrule 14.

Referring especially to FIG. 2, the tube T has been inserted through thenut bore 11, the ferrule 14, and into the body counterbore 9 in abuttingengagement with the internal shoulder 8, and the nut 5 has beenfinger-tightened on the body 1 so that the opposite ends of the ferrule14 are in engagement with the flare mouth 10 and the tapered internalshoulder 12 respectively.

The forward end portion 15 of the ferrule 14 is substantiallycylindrical, the cylindrical portion being of substantial length andhaving a radiused outer corner which initially engages flare mouth 10.The cylindrical portion 15 has a counterbore 16 which provides tworadially offset and axially spaced apart sharp corners 1'7 and 18 which,as hereinafter explained, are adapted to bite into the surface of thetube T and to plow up ridges or shoulders of the tube metal so toprovide fluid seals and strong holding shoulders which effectivelyresist pull-out of the tube T from the coupling assembly after the nuthas been tightened as in PEG. 3.

Adjacent the cylindrical portion 15 of the ferrule is an intermediatetapered portion 19, said taper being less than the taper of the bodyportion it the latter preferably being about 12 degrees and the taper oftheinterrnediate sleeve portion 1% being preferably about degrees. Theforward or small end of the tapered portion 1% is of smaller diameterthan the cylindrical portion and the large end of the tapered portion 1%is of greater diameter than the cylindrical section 15. The small end ofthe tapered portion 19 in effect provides a neck portion 1% adjacent thecylindrical portion 15 about which the cylindrical portion pivots as itis deformed by the body taper 1d.

Adjacent the thick end of such tapered portion, the ferrule 14 is formedwith a peripheral groove 2i? which provides another neck portion, andwith a radially enlarged head 21, the outer surface of which is taperedin a radially inward and axially outward direction as shown in FIG. 2.The outer or rear end of the ferrule 14 is preferably cut off square andthe inner corner 23 is generally rounded as shown.

Accordingly, as shown in FIG. 2, the outer corner of the head 21 of theferrule 14 has line contact with the internal tapered shoulder 12 of thenut 5 at a diameter which is preferably greater than the diameter ofcontact of the rounded corner 15a at the inner end of the ferrule 14with tthe flare mouth 10.

It can now be seen that when the nut 5 is in fingertight position, theferrule 14 will be positioned coaxially of the body 1 and nut 5 byreason of the engagement of the opposite ends thereof with thefrusto-conical tapered surfaces of the flare mouth it) and internalshoulder 12 and of course the tube T will be centered by counterbore 9and the through bore of ferrule 14.

When the nut 5 is tightened, the axial force exerted thereby around theline contact of the head 21 with the internal shoulder 12 will cause theferrule 14- to be axially advanced into the flare mouth it) therebycausing the enlarged cylindrical end portion to be progressivelydeformed as cantilever beams about neck 19 to frustoconical form, asclearly shown in FIG. 3, and first, the sharp corner 17 contacts thesurface of the tube T to progressively build up a. holding shoulder oftube metal, while at the same time the end of the tube T is firmlypressed against the internal shoulder 8 in the body 1. Finally, beforethe nut 5 has been tightened to the extent shown in FIG. 3, the othersharp corner 13 will, likewise, become embedded in the surface of thetube T to create a second sealing and holding shoulder 26. However, atthat time the entire cylindrical end portion of the ferrule 14 has beendeformed to frusto-conical form and into engagement with the tube T, andthe intermediate tapered portion 19 has arched slightly outwardly andadvanced into contact with the tapered flare mouth 10 whereby verylittle additional radial contraction of the initially cylindricalportion 15 will be effected thereafter even by application of asubstantially increased tightening torque on the nut 5.

When the nut 5 has been tightened to this extent there has been asubstantial force coupling (composed of radially offset axial forcesacting as indicated by the arrows) imposed on the head 21 of the ferrule14 which is effective to turn the head 21 inwardly about its zone ofengagement with the tapered internal shoulder 12 of the nut 5, wherebythe yielding or deformation of the ferrule at the region of theperipheral groove 2% will cause the bore portion in the head end of theferrule 14 to contract radially to provide a gradually releasingfrictional grip on the outer surface of the tube T to effectively resistor dampen vibrations; This prevents vibrations from causing failure ofthe tube T at or adjacent the holding shoul ders 2S and 26.

The apex angles or angles of taper of the flare mouth 1d and of theinternal shoulder 12 are of considerable importance to proper operationof the coupling in that to elfect desired biting action of the corners1'7 and 18 into the surface of the tube T to create the sealing andpullout resisting ridges or shoulders 25 and 26 requires a wedge-taperof the flare mouth 10 so that there will be a substantial forcemultiplication whereby a predetermined axial force on the ferrule 14will result in a much greater radial inward force component to causecontraction while the attitude of the corners 17 and 18 is such as toinduce a plowing action which progressively builds up the shoulders 2-5and 26 as the ferrule is thus am'ally advanced and radially contractedat its inner end. By the same token, the internal shoulder 12 in the nut5 is tapered to set up a radial wedge angle relationship with the outerend of the ferrule 14 so that as the coupling is being made up largeaxial forces may be exerted through the nut 5 without prematurelycontracting the outer end of the ferrule 14. This relationship at thehead 21 and shoulder 12 induces the aforedescribed swinging or tippingaction of the head 21 of the ferrule 14 about the outer zone of axialforce application with respect to the inner zone of axial reactingforces. Accordingly, the ferrule 14, by the time it has been properlycontracted into biting and sealing engagement with the tube T, is placedunder a high degree of axial compression which is sufficient to cause aradial contraction at the groove 29 thereof and consequent swinging inof the adjacent portion of the head 21 about the outer zone of axialforce application on said head.

By again referring to FIG. 3, it will be noted that under normaltightening the sleeve head 21 swings or tips so that the rear portion ofthe sleeve is contracted into vibration dampening contact with the tubeand the sleeve head is tipped to such an extent that the outer end faceof the sleeve head coincides with the shoulder surface 12 of the nut soas to establish full surface contact therebetween. This eliminates thecouple action referred to above so that further tightening of the nutresults in substantially no additional tipping or swinging in of thesleeve head. The bringing about of such surface contact has the effectof discontinuing or limiting such tipping and thus limits the amount ofcontraction of the sleeve head against the tube so that the tube will begripped tightly enough to prevent vibration strains on the tube fromreaching the sealing edges 17 and 18 but not tightly enough toobjectionally contract the tube or grip it so firmly that stressconcentrations will cause early failure at this region due to vibrationinduced stress concentrations.

By further reference to FIG. 3, it will be noted that with the front andrear sections of the sleeve contracted against the tube, the sleeve hasa somewhat arched configuration and that the contact of the body taper10 with the intermediate portion 19 prevents outward buckling of thelatter. Such arching also results in a spring action which tends to lockthe nut against loosening under vibration.

From the foregoing, it is clear that where the tube end is out offcleanly and squarely there may be a fluid-tight seal effected betweenthe end of the tube T and the internal shoulder 8 of the body 1. Furtherseals are obtained where the corners 17 and 18 of the ferrule 14- areembedded in the surface of the tube T and where the relatively initiallywide cylindrical surface 15 of the ferrule 14 is in intimate contactwith the flare mouth 10. Such wide area contact precludes gouging ordamage to the flare mouth 1% by the ferrule 14, whereby the body 1 maybe repeatedly assembled and disassembled and even be used with newferrules and tubes.

By way of example, the body 1, nut 5, and ferrule 14,

may be fabricated as of commercial brass for use with conventionalcopper tubing such as is used in automotive fiuid systems and inhydraulic systems in the machine tool art. Of course, other materialsmay be used depending upon the service to which the coupling assembly isto be put, and according to the material from which the tube T is made.Thus, for high pressure systems or systems handling corrosive fluids,the tube T may be of stainless steel, or the like, and in that case thebody 1, nut 5, and ferrule 14 likewise, will be made ofcorrosion-resisting material but pre erably at least the ferrule will bematerial which is harder than the tube T, so that the sharp corners 17and 13 will readily bite into the surface of the tube T to plow up thenecessary holding ridges 25 and 26.

By way of further example, couplings for /s, 3 A", /8, A2", A", and 1"tubing made in accordance With this invention should have the followingdimensions:

Taper of flare mouth 19 with respect to axis of body 1 to preferablyTaper of outer surface of head 21 Taper of internal shoulder 12Approximately 5 to 7.

10 to 15, preferably Taper of ferrule from neck 19a to groove 2%Preferably about 10 (usually 2 less than flare mouth 11)).

Length (end to neck 1%) to thickness ratio of cylindrical olfset end offerrule 14- Approximately 3: 1 to Ratio of thickness at cylindricalportion of ferrule 14 to thickness at neck 1 9a Ratio of thickness offerrule at groove to thickness at neck Approximately 1:1.

Approximately 1:1 to

about 1.5:1.

Ratio of radial distance from tube T to outer corner of head 21 toradial distance from, tube T to corner 15 Approximately 1521 to about2.2: 1.

Radial clearance from tube T to counterbore 16 Approximately .007 forA2" and larger sizes up to about .012 for 1 size.

Ratio of length of cylindrical portion 15 with tapered portion 19Approximately 1:1 to

about 111.5.

The foregoing relationships have been found well suited for joiningcommercial grades of copper tube T to couplings comprising bodies 1,nuts 5, and ferrules 14- made as of brass.

The radially offset relation of the axial forces as de noted by thearrows effects yet another important result and that is that there isresilient bending or swinging of the head 21 in a counterclockwisedirection as viewed in the drawings.

Upon loosening of nut there will be slight bending or swinging of thesleeve head in the opposite, i.e., clockwise, direction within tr eelastic limit of the sleeve head. Thus, there is a resilient contact ofthe sleeve head with the not for providing an additional sprin likeaction to resist loosening of the nut 5 by vibration or otherwise.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A flareless tube coupling comprising first and second threadedlyengaged coupling members defining a tube-end receiving cavitytherebetween including an annular space around the tube withcorresponding first and second tapered annular end walls that moveaxially toward each other when said members are screwed together; and atubular ferrule in such space, said ferrule being counterbored at theend adjacent said first end wall to provide a leading edge that has aradial clearance with the tube and being formed with a generallycylindrical portion of substantial length and substantially uniformradial thickness which is of a diameter greater than the axiallyadjoining part of the intermediate portion of said ferrule, saidintermediate portion having a taper of increasing radial thicknessterminating in a peripheral groove, and a head of larger diameter thansaid cylindrical portion and said groove extending from said groove tothe end of said ferrule, said head adapted to be initially contacted bysaid second end wall only along the periphery of its radially outeraxial end edge, whereby, when said members are screwed together, saidfirst end v all contracts end of said cylindrical portion forcing saidleading edge into gripping engagement with said tube and said second endwall swings said head about said groove to radially contract the headend of the ferrule against said tube, said second end wall coming intofull contact with the lateral end of said head.

2. A coupling according to claim 1 wherein said head has a gradual taperof increasing radial thickness from its end toward said groove.

3. A coupling according to claim 1 wherein said head is formed with arounded inner corner to provide a gradually decreasing engagement withthe tube in a direction axially toward said second end wall.

4. A coupling according to claim 1 wherein said intermediate taperedportion is engageable by said first end wall to resist furthercontraction of said cylindrical portion.

References Cited in the file of this patent UNITED STATES PATENTS2,179,127 Lauer Nov. 17, 1939 2,211,856 Kreidel Aug. 20, 1940 2,287,889Krumsiek June 30, 194-2 2,496,510 Wolfram Feb. 7, 1950 2,536,745 HeroldJan. 2, 1951 2,791,452 Watson May 7, 1957 2,943,871 St. Clair July 5,1960 FOREIGN PATENTS 688,744 Great Britain Mar. 11, 1953

1. A FLARELESS TUBE COUPLING COMPRISING FIRST AND SECOND THREADEDLYENGAGED COUPLING MEMBERS DEFINING A TUBE-END RECEIVING CAVITYTHEREBETWEEN INCLUDING AN ANNULAR SPACE AROUND THE TUBE WITHCORRESPONDING FIRST AND SECOND TAPERED ANNULAR END WALLS THAT MOVEAXIALLY TOWARD EACH OTHER WHEN SAID MEMBERS ARE SCREWED TOGETHER; AND ATUBULAR FERRULE IN SUCH SPACE, SAID FERRULE BEING COUNTERBORED AT THEEND ADJACENT SAID FIRST END WALL TO PROVIDE A LEADING EDGE THAT HAS ARADIAL CLEARANCE WITH THE TUBE AND BEING FORMED WITH A GENERALLYCYLINDRICAL PORTION OF SUBSTANTIAL LENGTH AND SUBSTANTIALLY UNIFORMRADIAL THICKNESS WHICH IS OF A DIAMETER GREATER THAN THE AXIALLYADJOINING PART OF THE INTERMEDIATE PORTION OF SAID FERRULE, SAIDINTERMEDIATE PORTION HAVING A TAPER OF INCREASING RADIAL THICKNESSTERMINATING IN A PERIPHERAL GROOVE, AND A HEAD OF LARGER DIAMETER THANSAID CYLINDRICAL PORTION AND SAID GROOVE EXTENDING FROM SAID GROOVE TOTHE END OF SAID FERRULE, SAID HEAD ADAPTED TO BE INITIALLY CONTACTED BYSAID SECOND END WALL ONLY ALONG THE PERIPHERY OF ITS RADIALLY OUTERAXIAL END EDGE, WHEREBY, WHEN SAID MEMBERS ARE SCREWED TOGETHER, SAIDFIRST END WALL CONTRACTS END OF SAID CYLINDRICAL PORTION FORCING SAIDLEADING EDGE INTO GRIPPING ENGAGEMENT WITH SAID TUBE AND SAID SECOND ENDWALL SWINGS SAID HEAD ABOUT SAID GROOVE TO RADIALLY CONTRACT THE HEADEND OF THE FERRULE AGAINST SAID TUBE, SAID SECOND END WALL COMING INTOFULL CONTACT WITH THE LATERAL END OF SAID HEAD.